如何获取表中行的小计计数？

Question

我有这个SQL查询吗？

SELECT COUNT(*) FROM PHRASE WHERE JLPT = 1
SELECT COUNT(*) FROM PHRASE WHERE JLPT = 2
SELECT COUNT(*) FROM PHRASE WHERE JLPT = 3
SELECT COUNT(*) FROM PHRASE WHERE JLPT = 4

有没有办法可以将这些查询合并为1，以便计算出有多少JLPT行的值为1,2,3＆amp; 4？

Answer 1

SELECT JLPT,
       COUNT(*)
FROM PHRASE
WHERE JLPT IN (1, 2, 3, 4)
GROUP BY JLPT;

Answer 2

如果您希望将这些值放在一行中，请使用条件聚合。

SELECT
    COUNT(CASE WHEN JLPT = 1 THEN 1 END) JLPT1,
    COUNT(CASE WHEN JLPT = 2 THEN 1 END) JLPT2,
    COUNT(CASE WHEN JLPT = 3 THEN 1 END) JLPT3,
    COUNT(CASE WHEN JLPT = 4 THEN 1 END) JLPT4
FROM PHRASE